The trend, especially for wind turbines or wind energy plants, particularly in the onshore area, is toward increasingly taller hub heights (the height at which the hub of the wind rotor is situated above the ground surface). Meanwhile, heights beyond 100 m are desirable here. In this way, higher and more constant wind speeds could be utilized and thus the efficiency of the wind turbine will be improved, especially in low wind areas.
But taller towers with larger and more powerful generators or rotors at the same time mean that the wall thicknesses and the diameters of the tower segments must be larger in order to meet the resulting greater demands of structural mechanics, such as rigidity, buckling resistance, and fatigue strength.
The problem here is, however, that, for logistical and transportation reasons, the transport of corresponding tower segments is no longer possible, due to restrictions such as bridge clearance height, when the dimensions of the individual tower segments are increased because of taller towers.
For this reason, towers of the kind mentioned above for wind turbines have been proposed in the prior art. Thus, for example, WO 2005/021897 A1 describes a tower with an upper tubular tower portion and a lower tower portion designed as a lattice tower.
However, it turns out that considerable drawbacks occur with such designs in terms of ergonomics and work safety, since in particular the accessibility of individual parts of the tower may be significantly impaired on account of the lattice construction in the lower tower portion. Furthermore, it turns out that the structural design of the lattice tower may be costly in such a hybrid design, since it must be designed to withstand large forces. This may lead to high expense and high costs.
Thus a need exists for a tower for wind turbines and a wind turbine that afford on the one hand an improved ergonomics and work safety and on the other hand make possible a structural design with optimized forces.